Tattooed Mage

Because paper is such a weak medium in the face of salt and spray, they tattoo their spells onto their body, turning skin to spellbook. 

Written in Blood

Starting at level 2 when you choose this school, you gain the ability to tattoo spells onto your allies temporarily. This process takes 10 minutes of uninterrupted work, and the creature being tattooed must be willing. 

At the end of the 10 minute tattoo process, choose a wizard spell you have prepared and expend a spell slot equal to that spell’s level. Until the end of their next long rest, the tattooed creature can cast that spell using your spellcasting modifier and proficiency bonus (note: if the tattooed creature can already cast spells, this does not allow them to cast the tattooed spell using their normal spell slots).  

The spell still originates from them, and they make all relevant decisions about the casting. Once they cast the spell the tattoo is expended and fades away. Until the recipient casts the spell, your spell slot remains expended. You can tattoo a number of spells equal to your Constitution modifier at one time, and no individual spell can be higher than 5th level. 

A creature can receive more than one spell tattoo.

Sun Tanned Hide

At 6th level, you become proficient in Constitution saving throws.

Hold Fast

After reaching 10th level, whenever you or one of your allies within 30 feet would be affected by a type of damage, you can use your reaction and expend an unused spell slot. If you do so, all allies within 30 feet of you gain resistance to that type of damage for 1 round per level of the spell slot expended.

Focus on the Pain

At 14th level, you gain the ability to inscribe a tiny part of your consciousness into a tattoo somewhere on your body. You can activate this ability whenever you cast a spell that requires concentration. For 1 minute, you can concentrate on two spells or abilities at the same time. Once the duration expires, you cannot use it again until you complete a long rest.